Competition kinetics of OH radical reactions with oxygenated organic compounds in aqueous solution: rate constants and internal optical absorption effects

2018 ◽  
Vol 20 (16) ◽  
pp. 10939-10948 ◽  
Author(s):  
T. Schaefer ◽  
H. Herrmann
Keyword(s):  
Aqueous Solution ◽  
Optical Absorption ◽  
Organic Compounds ◽  
Aqueous Phase ◽  
Rate Constants ◽  
Radical Reactions ◽  
Solution Rate ◽  
Oh Radical ◽  
Kinetics Of

Atmospheric aqueous phase rate constants are determined and the effect of optical absorbers in competition kinetics is studied.

Investigation of OH radical kinetics with glycine, alanine, serine and threonine in the aqueous phase

2021 ◽  
Author(s):  
Liang Wen ◽  
Thomas Schaefer ◽  
Hartmut Herrmann
Keyword(s):  
Amino Acids ◽  
Aqueous Phase ◽  
Rate Constants ◽  
Density Functional ◽  
Flash Photolysis ◽  
Biological Activities ◽  
Radical Reaction ◽  
Atmospheric Effects ◽  
Oh Radical ◽  
Kinetics Of

<p>Amino acids are key substances in biological activities and can be emitted into the atmosphere as constituents of primary aerosols. Understanding the radical kinetics of amino acids is necessary to evaluate their atmospheric effects. In the present study, the hydroxyl radical (OH) reaction kinetics of glycine, alanine, serine and threonine were investigated in the aqueous phase. The temperature and pH dependent rate constants were measured by a laser flash photolysis-long path absorption setup using the competition kinetics method. Based on the measurements and speciation calculations, the OH radical reaction rate constants of the fully protonated (H<sub>2</sub>A<sup>+</sup>) and neutral (HA<sup>±</sup>) form were determined. The following T-dependent Arrhenius expressions were derived for the OH radical reactions with glycine, <em>k</em>(<em>T</em>, H<sub>2</sub>A<sup>+</sup>) = (9.1 ± 0.3) × 10<sup>9</sup> × exp[(-2360 ± 230 K)/<em>T</em>], <em>k</em>(<em>T</em>, HA<sup>±</sup>) = (1.3 ± 0.1) × 10<sup>10</sup> × exp[(-2040 ± 240 K)/<em>T</em>]; alanine, <em>k</em>(<em>T</em>, H<sub>2</sub>A<sup>+</sup>) = (1.0 ± 0.1) × 10<sup>9</sup> × exp[(-1030 ± 340 K)/<em>T</em>], <em>k</em>(<em>T</em>, HA<sup>±</sup>) = (6.8 ± 0.4) × 10<sup>10</sup> × exp[(-2020 ± 370 K)/<em>T</em>]; serine, <em>k</em>(<em>T</em>, H<sub>2</sub>A<sup>+</sup>) = (1.1 ± 0.1) × 10<sup>9</sup> × exp[(-470 ± 150 K)/<em>T</em>], <em>k</em>(<em>T</em>, HA<sup>±</sup>) = (3.9 ± 0.1) × 10<sup>9</sup> × exp[(-720 ± 130 K)/<em>T</em>]; and threonine, <em>k</em>(<em>T</em>, H<sub>2</sub>A<sup>+</sup>) = (5.0 ± 0.1) × 10<sup>10</sup> × exp[(-1500 ± 100 K)/<em>T</em>], <em>k</em>(<em>T</em>, HA<sup>±</sup>) = (3.3 ± 0.1) × 10<sup>10</sup> × exp[(-1320 ± 90 K)/<em>T</em>] (in units of L mol<sup>-1</sup> s<sup>-1</sup>).</p> <p>The density functional theory calculation was performed using GAUSSIAN to simulate the energy barriers (<em>E<sub>Barrier</sub></em>) of OH radical induced H-atom abstraction. According to the simulated results, amino and carboxyl group increase the <em>E<sub>Barrier</sub></em> at the adjacent C‑atom and thus reduce the OH radical reactivity. Hydroxide and methyl group decrease the <em>E<sub>Barrier</sub></em> at the adjacent C-atom, leading to an increase in the OH radical rate constant.</p>

Ferricyanide Oxidation of Butanol Homogeneously Catalysed by Chlororuthenium Complexes

1979 ◽  
Vol 32 (9) ◽  
pp. 1905 ◽  
Author(s):  
AF Godfrey ◽  
JK Beattie
Keyword(s):  
Aqueous Solution ◽  
Complex Formation ◽  
Linear Dependence ◽  
Rate Constants ◽  
Homogeneous Catalyst ◽  
Basic Solution ◽  
Rate Law ◽  
Kinetics Of ◽  
Solution Estimates ◽  
Butanol Concentration

The oxidation of butan-1-ol by ferricyanide ion in alkaline aqueous solution is catalysed by solutions of ruthenium trichloride hydrate. The kinetics of the reaction has been reinvestigated and the data are consistent with the rate law -d[FeIII]/dt = [Ru](2k1k2 [BuOH] [FeIII])/(2k1 [BuOH]+k2 [FeIII]) This rate law is interpreted by a mechanism involving oxidation of butanol by the catalyst (k1) followed by reoxidation of the catalyst by ferricyanide (k2). The non-linear dependence of the rate on the butanol concentration is ascribed to the rate-determining, butanol-independent reoxidation of the catalyst, rather than to the saturation of complex formation between butanol and the catalyst as previously claimed. Absolute values of the rate constants could not be determined, because some of the ruthenium precipitates from basic solution. With K3RuCl6 as the source of a homogeneous catalyst solution, estimates were obtained at 30�0�C of k1 = 191. mol-1 s-1 and k2 = 1�4 × 103 l. mol-1 s-1.

Reaction kinetics of OH radicals with glutaric acid and adipic acid in the aqueous phase

2021 ◽  
Author(s):  
Liang Wen ◽  
Thomas Schaefer ◽  
Hartmut Herrmann
Keyword(s):  
Aqueous Phase ◽  
Adipic Acid ◽  
Rate Constants ◽  
Density Functional ◽  
Glutaric Acid ◽  
Radical Reaction ◽  
Basis Set ◽  
Oh Radicals ◽  
Oh Radical ◽  
Energy Barriers

<p>Dicarboxylic acids (DCAs) are widely distributed in atmospheric aerosols and cloud droplets and are mainly formed by the oxidation of volatile organic compounds (VOCs). For example, glutaric acid and adipic acid are two kinds of the DCAs that can be oxidized by hydroxyl radical (‧OH) reactions in the aqueous phase of aerosols and droplets. In the present study, the temperature- and pH-dependent rate constants of the aqueous OH radical reactions of the two DCAs were investigated by a laser flash photolysis-long path absorption setup using the competition kinetics method. Based on speciation calculations, the OH radical reaction rate constants of the fully protonated (H<sub>2</sub>A), deprotonated (HA<sup>-</sup>) and fully deprotonated (A<sup>2-</sup>) forms of the two DCAs were determined. The following Arrhenius expressions for the T-dependency of the OH radical reaction of glutaric acid, k(T, H<sub>2</sub>A) = (3.9 ± 0.1) × 10<sup>10</sup> × exp[(-1270 ± 200 K)/T], k(T, HA<sup>-</sup>) = (2.3 ± 0.1) × 10<sup>11</sup> × exp[(-1660 ± 190 K)/T], k(T, A<sup>2-</sup>) = (1.4 ± 0.1) × 10<sup>11</sup> × exp[(-1400 ± 170 K)/T] and adipic acid, k(T, H<sub>2</sub>A) = (7.5 ± 0.2) × 10<sup>10</sup> × exp[(-1210 ± 170 K)/T], k(T, HA<sup>-</sup>) = (9.5 ± 0.3) × 10<sup>10</sup> × exp[(-1200 ± 200 K)/T], k(T, A<sup>2-</sup>) = (8.7 ± 0.2) × 10<sup>10</sup> × exp[(-1100 ± 170 K)/T] (in unit of L mol<sup>-1</sup> s<sup>-1</sup>) were derived.</p><p>The energy barriers of the H-atom abstractions were simulated by the Density Functional Theory calculations run with the GAUSSIAN package using the M06-2X method and the basis set m062x/6-311++g(3df,2p). The results showed that the energy barriers were lower at the C<sub>β</sub>-atoms and are higher at the C<sub>α</sub>-atoms of the two DCAs, clearly suggesting that the H-atom abstractions occurred predominately at the C<sub>β</sub>-atoms. In addition, the ionizations can enhance the electrostatic effects of the carboxyl groups, significantly reducing the energy barriers, leading to the order of OH radical reactivity as  <  < . This study intends to better characterize the losing processes of glutaric acid and adipic acid in atmospheres.</p>

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